The present invention relates to a device incorporated in a copier, facsimile transceiver, printer or similar image recorder for removing the curl of a recording sheet.
A curl removing device for the above application has beem proposed in various forms in the past. For example, Japanese Patent Publication No. 11792/1975 discloses a device having an elastic roller whose surface layer is made of an elastic material such as rubber or sponge, and a hard roller pressed against the elastic roller. A recording sheet with a curl is passed through between the elastic roller and the hard roller with the outer side thereof with respect to the direction of curl facing the hard roller. Since the amount of curl of a recording sheet depends on the material and the moisture content of the sheet. the force to act on the sheet for straightening it has to be changed in matching relation to the amount of curl. The conventional curl removing devices including the device disclosed in the above-mentioned Japanese Patent Publication cannot meet this requirement. Specifically, it is likely with the conventional devices that a recording sheet with a noticeable curl fails to have the curl removed sufficiently while a recording sheet with a small curl is caused to curl in the other direction.